Covers of the type in which a traveling element can project through the cover, and in which the cover effectively protects the elongated element, while still permitting movement of the projecting element, have previously been proposed. Such covers may have a closure which has an elongated slit, with edges formed similar to a slide fastener edge. One edge may have a longitudinally extending groove into which a longitudinally extending rib can engage, the movable element projecting between the groove and the rib when they are separated, the groove and the rib splitting in advance of the transversely projecting element as it moves, and reclosing therebehind.
A protective cover of this type has been described in German Pat. No. Publication U-18 83 255. This structure is designed particularly for elongated scales secured to machine tools to protect the scales against contamination and deposit of oil and oily residues and substances and the like thereon. The cover is formed of two foil-like strips which are joined together similar to a slide fastener, attached at their edges to the bed of the machine which carries the scale. This requires the bed of the machine to be constructed with a longitudinal groove or the like, or with projecting ribs located at both sides of the scale rod in order to permit attachment of the foils, and to space the foils from the scaling rod. Such a cover is not suitable for use with moving elements, such as spindles, shafts or feed screws.
Cross slides or supports which are driven by feed screws in parallel with the bed of a machine tool preferably should be protected against contamination, dirt, splashing oil and the like. The feed screws or spindles, thus, should be covered throughout their length. Feed spindles, particularly of precision machine tools, are also subject to damage or inaccuracies in operation by chips and spirals of cut material removed in machining operation, and carried about, for example, by cooling fluids. Protective covers have been proposed which still permit passage of a drive element for a cross slide thereto by leaving open regions through which the cross slides can pass. Such covers all have the disadvantage that gaps are left through extended portions of the spindle through which contaminants may enter.
It has been proposed to cover spindles, columns, feed screws and the like by placing bellows therearound. The bellows, in order to accomodate the substantial length, will have a substantial diameter when collapsed, so that the ratio of outer diameter to the diameter of the feed screw or spindle or element which they are protect is undesirable. In order to obtain a reasonable length of bellows, when extended, the outer diameter becomes so large that difficulties in placement of spindles and drive feeds will result. Further, if the stroke of the traversing element, for example a cross slide, is long, the bellows must be spaced from the moving cross slide or feed screw from the inside by spacing spiders, or from the outside by means of holders and guide eyes. These structures are space-consuming and frequently cause operating difficulties. It has also been proposed to use spiral-spring covers which include a spiral spring wound about itself and made of hardened sheet spring steel, surrounding the spindle, and collapsing into itself upon movement of the cross slide on the spindle. Such spiral spring covers cannot be introduced into machine tools without additional attachment fittings. They cannot be placed independently of the position of the spindle to be protected. For example, if such a spiral is installed in a vertical position, some arrangement must be made to prevent collapse of the spiral loops within each other and spreading of spiral loops; the protective function would then not obtain. Additionally, as the spiral spring is extended, a rotary or twisting movement will result which must be compensated for by suitable bearing flanges at the ends of the spiral spring. Longer spindles can be protected only by coupled multiple or stacked spiral springs. The arrangement and placement of such elements is complex and expensive.
It has also been proposed to cover elongated machine elements using high-quality rust-resistant or rust-free spring steel or plastic material in form of a tape or ribbon which is wound, in spiral manner, on the spindle to be protected, and which is guided in the region of the cross slide over deflection rollers, around the cross slide or spindle nut. Upon relative rotation between the spindle nut and the spindle, the ribbon or tape will wind off from one side and wind on on the other, in dependence on the direction of rotation of the spindle, and the direction of thread cut. The width of the covering tape or ribbon must correspond to the pitch of the thread of the spindle which is to be protected. Consequently, different cover tapes must be provided for different feed screw pitch dimensions. Reliable winding-off and winding-on of the cover tape can be assured only if longitudinal stretching of the cover tape is compensated by a tensioning device which, together with the deflection rollers, must be in turn protected by a separate housing in order to prevent interference with proper rolling-off and rolling-on of the tape or ribbon. The entire structure is complex and requires a substantial number of components.